1. Field of the Invention
The present invention relates to a method of automatically regulating the timing of operation of the chopper blade of a chopper-type folding device incorporated into a rotary printing press, and an automatic chopper blade operating timing regulator for carrying out the same.
2. Description of the Prior Art
A web-fed rotary printing press is provided with a folding machine for cutting a printed, dried and cooled web into sheets of a predetermined length and for folding the web lengthwise or widthwise. The folding machine operates in a former fold mode to fold a web once widthwise before the web is cut, in a parallel folio fold mode to fold a sheet once in a signature, in a parallel quarto fold mode to fold a sheet twice in a quarto sheet or in a chopper fold mode to fold a parallel-folded sheet along a direction perpendicular to the fold with a chopper blade. One of those folding modes or a combination of some of those folding modes is selected according to a required folding specification.
A chopper-type folding device stops, locates and adjust the squareness of a sheet being conveyed by conveyor belts by a locating plate, folds the sheet along its center line in a signature with a plate-shaped chopper blade by lowering the chopper blade perpendicularly to the sheet and pressing the sheet in a space between gripper rollers disposed under the chopper blade.
FIG. 2 is a diagrammatic side view of a folding machine provided with two sets of chopper-type folding devices, and FIG. 3 is a diagrammatic view taken in the direction of arrows along the line III--III in FIG. 2.
Referring to FIG. 2, there are shown a web 11, a cutting cylinder 12, a folding cylinder 13, a gripping cylinder 14, an intermediate transfer cylinder 15, an upper transfer cylinder 16, a lower transfer cylinder 17, an upper chopper-type folding machine 18, and a lower chopper-type folding machine 19. The web 11 held between the cutting cylinder 12 and the folding cylinder 13 is cut into a sheet of a predetermined length by a cutting blade 20 provided on the cutting cylinder 12, and the sheet is held with needles 21 provided on the folding cylinder 13 so as to lap around the lower half circumference of the folding cylinder 13. The sheet held by the needles 21 is folded in a signature with an inserting knife 22 provided on the folding cylinder 13 and the signature is gripped with a gripping plate 23 provided on the gripping cylinder 14 so as to lap around the upper half circumference of the gripping cylinder 14, and then the signature is transferred from the gripping plate 23 to to gripping fingers 24 provided on the intermediate transfer cylinder 15. Folios thus formed are transferred alternately to the upper transfer cylinder 16 and the lower transfer cylinder 17 from the intermediate transfer cylinder 14 so as to be gripped with gripping fingers 25 and 16 provided respectively on the upper transfer cylinder 16 and the lower transfer cylinder 17. Then, the signatures are delivered to the upper chopper-type folding device 18 from the upper transfer cylinder 16 and to the lower chopper-type folding device 19 from the lower transfer cylinder 17.
As shown in FIGS. 2 and 3, the signature is conveyed along the upper surface of a plate 33 by conveyor belts 32 wound around tension pulleys 31 until they are stopped by a locating plate 34. The table 33 is provided with a slit 35 extending in the direction of travel of the signature in the central portion thereof with respect to the width. Guide plates 36 are attached to the edges of the plate 33 opposite to each other to guide the signature downward through the slit 35. A pair of upper delivery rollers 37 and 38, and a pair of lower delivery rollers 39 and 40 are disposed in that order under the guide plates 36. The delivery rollers 37, 18, 29 and 40 are driven for rotation by driving means, not shown, in the direction of arrows shown in FIG. 3. A chopper blade 41 is attached to the extremity of a swing lever 42 supported for swing motion on a shaft 43. The chopper blade 41 is located above the guide plates 36 in alignment with the slit 35. The shaft 43 is driven by driving means, not shown in synchronism with the conveyance of the signature to lower the chopper blade 41 substantially vertically into the slit 35 between the guide plates 36.
The signature conveyed along the upper surface of the plate 33 is stopped and located in correct squareness by the locating plate 34, and then the chopper blade 41 is lowered to fold the signature in a quarto sheet and to insert the quarto sheet between the delivery rollers 37 and 38. The quarto sheet is pressed between the upper delivery rollers 37 and 38 and between the lower delivery rollers 39 and 40 to fold the quarto sheet exactly. Then, the quarto sheet is transferred to a delivery unit.
The chopper-type folding device 18 (19) stops the signature and corrects the misalignment of the signature attributable to the difference in stiffness between a portion of the signature near the fold and a portion of the same remote from the fold by the locating plate 34 to locate the signature in a correct squareness for folding.
Thus, the chopper-type folding device actuates the chopper blade 41 to fold the signature after locating the signature by the locating plate 34. If the chopper blade 41 is operated at regular intervals, the signatures must be delivered at regular intervals. Therefore, the mode of impact of the signature on the locating plate 34 is dependent on the basis weight of the sheet, the width of the sheet the number of webs and the printing speed of the web-fed rotary printing press. An excessively high impact of collision between the signature and the locating plate 34 will crush the leading edge of the signature to deteriorate the quality of a signature. If the chopper blade 41 is actuated before the signature reaches the locating plate 34, the signature will be folded incorrectly.
Therefore, the chopper-type folding device is provided with a timing device for timing the operation of the chopper blade 41. A conventional timing device is operated manually by the operator to adjust the timing of operation of the chopper blade 41 observing the mode of collision of the signatures against the locating plate 34. Therefore a considerable number of waste sheets are produced during timing adjustment, and the quality of the signature is affected greatly by the level of skill of the operator. Furthermore, the timing must be adjusted every time the printing speed or the description of web is changed, which affects adversely to the productivity of the web-fed rotary printing press.